1. Field of the Invention
The present invention relates to magnetic detecting elements in which the magnetization of a free magnetic layer is controlled by an exchange bias technique, and particularly to a magnetic detecting element exhibiting a stable, large reproduction output even with a narrow track width and in which side reading can be suppressed, and to a method for manufacturing the same.
2. Description of the Related Art
FIG. 29 is a fragmentary sectional view of a known magnetic detecting element (spin-valve thin-film element), viewed from a side opposing a recording medium.
This magnetic detecting element includes a first antiferromagnetic layer 1 formed of a PtMn alloy or the like, and a pinned magnetic layer 2 formed of a NiFe alloy or the like, a nonmagnetic material layer 3 formed of Cu or the like, a free magnetic layer 4 formed of a NiFe alloy or the like, and a nonmagnetic interlayer 5 formed of Ru or the like are deposited on the first antiferromagnetic layer 1 in that order.
Also, sets of a ferromagnetic layer 6, a second antiferromagnetic layer 7, and an electrode layer 8 are formed on the nonmagnetic interlayer 5, separated by a space having a track width Tw in the track width direction (X direction shown in the figure), as shown in FIG. 29.
Such magnetic detecting elements as shown in FIG. 29 have been disclosed in Japanese Unexamined Patent Application Publication Nos. 2001-155313 (pp. 12–13, FIG. 1) and 2001-339111 (p. 10, FIG. 1).
In the magnetic detecting element shown in FIG. 29, the magnetization of the ferromagnetic layer 6 is fixed in the X direction by an exchange coupling magnetic field generated at the interface between the second antiferromagnetic layer 7 and the ferromagnetic layer 6. The magnetization of the free magnetic layer 4 is fixed in the X direction by RKKY interaction acting between the ferromagnetic layers 6 and the free magnetic layer 4 separated by the nonmagnetic interlayer 5, in both end portions of the element. The free magnetic layer 4 in the central portion of the element is put into a single magnetic domain state to such a small extent that the magnetization thereof is reversible in response to an external magnetic field.
This technique for controlling the magnetization of the free magnetic layer 4 is referred to as the exchange bias method. In particular, in the magnetic detecting element shown in FIG. 29, the free magnetic layer 4 and the ferromagnetic layer 6 are put into an artificial ferromagnetic state. It has therefore been considered that the magnetization of the free magnetic layer 4 is certainly fixed in the end portions of the element to maintain its single magnetic domain state.
Accordingly, it has been expected that the structure shown in FIG. 29 would reduce hysteresis and Barkhausen noise.
However, since, in the magnetic detecting element shown in FIG. 29, the ferromagnetic layers 6 have internal side surfaces 6a, magnetic charge occurs at the internal side surfaces 6a and this surface magnetic charge generates a static magnetic field.
The direction of the static magnetic field is designated by arrows in FIG. 29. Specifically, the static magnetic field is oriented in the inverse direction to the magnetization direction of the free magnetic layer 4 and, consequently, the magnetization of the free magnetic layer 4 is disordered.
Consequently, the hysteresis cannot be reduced even though the ferromagnetic layers 6 are provided as shown in FIG. 29, and possibility of the occurrence of Barkhausen noise is maintained. Further improvement has been desired.